Although usable for any bearings, the present invention, as well as the problem underlying the invention, are explained in more detail with reference to a pivot bearing of an aircraft, which connects a rudder unit to a rudder in an articulated manner.
An example of such a pivot bearing known to the applicant is shown in FIG. 8 in a perspective view and in FIG. 9 in a perspective sectional view C-C of FIG. 8.
A connecting arrangement 1 for connecting a rudder to a rudder unit of an aircraft in an articulated manner comprises a bearing fitting 2 associated with the rudder and a bearing fork 3 associated with the rudder unit, which are fastened to one another in an articulated manner via a pivot bearing 4. As may be seen in FIG. 9, the pivot bearing 4 comprises a spherical bearing internal part 6 fixedly provided on a bearing bolt 5, which is in sliding connection with a shell-shaped bearing external part 7 fixedly provided on the bearing fitting 2. Retaining means 8, 9, 10 are provided in order to retain the bearing bolt 5 as well as the bearing internal part 6 releasably on the bearing fork 3. When the rudder is deflected, the bearing external part 7 pivots about the bearing internal part 6.
Wear in the pivot bearing 4, in particular, may result in linear mobility between the bearing internal part 6 and the bearing external part 7. This is referred to as bearing clearance and has to be monitored at regular intervals, in order to ensure functional reliability of the aircraft. Too much bearing clearance may result in, for example, vibrations, loss of comfort, control problems, or even loss of the rudder unit during the operation of the aircraft.
Currently, the bearing clearance is tested by an experienced mechanic, who manually shakes the rudder and judges according to his intuition and experience, whether an impermissibly large bearing clearance is present. Such manual testing is very inaccurate. As a result, for example, it may lead to premature replacement of bearings, which leads to high costs. Alternatively, however, a faulty pivot bearing is not replaced and this results in control problems of the aircraft during operation.
A further difficulty is that, in principle, a plurality of the connecting arrangements shown in FIGS. 8 and 9 are provided concentrically above one another, said connecting arrangements connecting the rudder at a plurality of points to the rudder unit in an articulated manner. For the mechanic, it is not possible simply by shaking to determine which of the plurality of pivot bearings has increased bearing clearance. This is because by shaking the rudder the mechanic applies force to all the bearing external parts and not simply to a single bearing external part. In case of doubt, all pivot bearings consequently have to be removed and/or the rudder dismantled and individually tested. This leads, however, with regular maintenance work, to high costs and is only possible with specific, costly equipment.